In the copending application by E. A. J. Marcatili entitled "Velocity Matched Optical Gate," Ser. No. 58,744, filed July 18, 1979, (now U.S. Pat. No. 4,251,130) a travelling-wave, velocity-matched optical gate (TW-VMG) is described wherein a travelling electrical signal is employed to locally control the coupling characteristic along an optical directional coupler. In particular, it is shown that ultrafast gating can be realized by means of a simple sine wave when the electric signal travels in synchronism with the optical signal.
To avoid spurious coupling effects, the electric signal path is advantageously terminated by means of a matching impedance. In this manner, reflections at the termination are avoided. It has been found, however, that it is relatively difficult to terminate the electric signal path in a manner which completely avoids reflections. In addition, when terminated in this manner, the electric circuit continuously consumes relatively large amounts of signal power.